The present invention relates to a door truck. It is known in the prior art to use metal wheels in a door truck which transports a sliding door hanging beneath the door truck. The use of a metal wheels causes high wear on a track which shortens the life of the track. Prior art door trucks use pendants which extend from the truck and are difficult to adjust.
It is an object of the present invention to provide a door truck which has plastic wheels and which includes a one piece frame designed to support the pendant below the track.
It is another object of the invention to provide an improved door truck which has wheels made of plastic which run quieter and eliminate the need for separate bearings for each wheel. The plastic wheels are also softer then steel wheels and extend the life of the door track.
It is a further object of the present invention to provide an improved pendant in a door truck which can be adjusted outside of the confines of the track. The pendant has flat sides on the head and also flat sides on the threaded body so that wrenches can be used to turn or hold the pendant so that it can be installed either with the head up or with the head down.
It is an object of the present invention to provide an improved door truck which can be simply assembled by merely screwing barrel nuts on a threaded stud. This eliminates the need for expensive processes such as welding, staking or riveting which are needed with prior art designs.
A door truck according to the invention has a one piece frame and has four wheels made of Acetal or similar plastic which allow the truck to operate quieter and eliminates the need for separate bearings for the wheels. The plastic wheels are also softer than steel which is used in prior art trucks and extend the life of the track.
The invention utilizes one barrel nut for each wheel. There are four wheels in each door truck. The barrel nuts pass through the plastic wheels and are connected together by a threaded stud that has no threads on the leading edges so that they will slip into the barrel nuts and position the parts for ease of assembly. The center of the stud is not threaded which causes the stud to center itself when the nuts are tightened. Other designs such as knurled threads could be used at the center to cause the stud to center itself. An alternative to two barrel nuts and a threaded stud is to use a barrel nut with an extended male threaded end which fits into the threaded interior of a second barrel nut.
Since in the present invention it is not necessary to weld or heat the frame during assembly, the parts can be plated, as for example, by zinc plating before assembly. In the prior art devices, if the frame were plated before assembly, welding which is required in such prior art devices would destroy the corrosion protection since the zinc or other plating burns off.
The present invention provides a design of a door truck which allows flexibility during installation because the pendant is arranged to fit the needs of a particular door.
The pendant may be installed with the threads down so that the threads are accessible below the track rather than in the track where they are not accessible. When installed in this manner, the pendant can be turned to adjust the height of the door by screwing it in and out of a threaded hole in the top of the door. The pendant may also be installed with the threads up, and the head of the pendant then holds the door. Nuts at the top can then be turned to adjust the height of the door. Flat sides on the pendant are used to keep the pendant from turning while the nuts are turned. An additional feature is that the top end of the pendant can project up into the track which allows the top of the door to be very close to the bottom of the track.
Other objects, features and advantages of the invention will become apparent from the following description and claims when read in view of the drawings in which: